We don't let Ly sleep in hers yet, im a bit of a pannicky mom lol. She wears it all day though, and as the beads are knotted between, if the string breaks the beads wont come off and cause choking/ be annoyong to clear up.
I must say, her's is fantastic. I bought it, and 2 days later, her first tooth was through, and I didnt even know til I felt it! Then just last week, tooth number 2 came through! So thats 2 teeth within 3 weeks, and she has not cried once over it, she has slept the best she ever has, 12 hours straight each night.
I swear by these necklaces!

Mine was from the exact same seller as the 2nd one and its not fake dont worry, it came with a leaflet and everything about baltic amber, and if you look at the beads, you can see they arent plastic, the only plastic bit is the screw catch mechanism.

If mine is fake (which it's not lol) I think plastic is the new baltic amber since it works brilliantly.
x

edit- the polished stone's tend to be around the £10 mark, the amber chips tend to be cheaper but dont look as nice IMO